O,O,O',O'-tetraoctyl-(branched and linear) S,S'-{methylenebis[imino(3-oxopropane-3,1-diyl)]} bis(phosphorothioate)

Long-term toxicity to aquatic invertebrates

Description of key information

The 21-Day EL50 (immobilization) value, based on nominal test concentrations, for the parental Daphnia generation (P1) was estimated to be greater than 100 mg/L loading rate WAF.
The 21-Day EL 50 (reproduction) value based on nominal test concentrations was estimated to be greater than 100 mg/L loading rate WAF.
The "No Observed Effect Loading Rate" was considered to be 100 mg/L loading rate WAF on the basis that at this test concentration there were no significant mortalities (immobilization) observed in the parental generation (P1) and that there were no significant differences (P> =0.05) between the control and the 100 mg/L loading rate WAF test group in terms of numbers of live young produced per adult by Day 21.

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates

Effect concentration:

100 mg/L

Additional information

In a key study performed to assess the chronic toxicity of the test item to Daphnia magna, the method followed was designed to be compatible with the OECD Guidelines for Testing of Chemicals (2008) No 211, "Daphnia magna Reproduction Test" referenced as Method C.20 of Commission Regulation (EC) No. 440/2008 and the US EPA Draft Ecological Effects Test Guidelines OPPTS 850.1300 "Daphnid Chronic Toxicity Test".

Due to the low aqueous solubility and complex nature of the test item, for the purposes of the test, the test item was prepared as a Water Accommodated Fraction (WAF).

Based on the results of a preliminary range finding test, Daphnia magna were exposed (10 replicates of a single daphnid per group) to a Water Accommodated Fraction (WAF) of the test item at a single nominal loading rate of 100 mg/L for a period of 21 days. The test solutions were renewed 3 times per week. The numbers of live and dead adult Daphnia and young daphnids (live and dead) were determined daily. The Daphnia were fed daily with a mixture of algal suspension and Tetramin® flake food suspension.

Chemical analysis of the freshly prepared test preparations showed measured concentrations to range from less than the Limit of Quantification (LOQ) of the analytical method, determined to be 0.010, to 1.11 mg/L. Chemical analysis of the aged preparations showed measured test concentrations to range from less that the LOQ to 0.464 mg/L.

Given that toxicity cannot be attributed to a single component or mixture of components, but to the test item as a whole, the results were based on nominal loading rates only.

The 21-Day EL50 (immobilization) value, based on nominal test concentrations, for the parental Daphnia generation (P1) was estimated to be greater than 100 mg/L loading rate WAF.

The 21-Day EL 50 (reproduction) value based on nominal test concentrations was estimated to be greater than 100 mg/L loading rate WAF.

The "No Observed Effect Loading Rate" was considered to be 100 mg/L loading rate WAF on the basis that at this test concentration there were no significant mortalities (immobilization) observed in the parental generation (P1) and that there were no significant differences (P> =0.05) between the control and the 100 mg/L loading rate WAF test group in terms of numbers of live young produced per adult by Day 21.

The "Maximum Acceptable Toxicant Loading Rate" was calculated to be 100 mg/L loading rate WAF.

It was considered unnecessary and unrealistic to test loading rates in excess of 100 mg/L.